Got to love new generation products, ha!
I would like to recommend you spend $.50 at Walmart at buy a Blitz Flex Nozzle. They are truly unique, not to mention cheap, and handle the job on the Onan easily. The nozzle fits the quart and gallon jugs. You screw it on, pull the nozzle up to extend it, bend it to a horseshoe and it will go right in the hole - no mess at all. I have used the marine pump, and hose taped to the bottle, etc., but this little ole cheapie is the real deal. I now have a dozen, carry one in the B for when someone mentions the Onan. Safe travels.